WO2004020228A1

WO2004020228A1 - An amphibious vehicle

Info

Publication number: WO2004020228A1
Application number: PCT/GB2003/003787
Authority: WO
Inventors: Alan Timothy Gibbs
Original assignee: Gibbs Technologies Ltd
Priority date: 2002-08-30
Filing date: 2003-08-29
Publication date: 2004-03-11
Also published as: GB2392415A; GB0320374D0; AU2003282210A1; EP1581402A1; GB0220164D0

Abstract

Amphibious vehicle (1) has a longitudinally mounted engine (18') and a hull (4) conformed to enable planing. Road wheels (3) have drag reduction means. They may be retractable, as shown; or faired. The engine has an output shaft aligned fore and aft in the vehicle, arranged to drive a gearbox having a reversible output, which in turn drives at least some of the road wheels and one or more marine propulsion units. The road wheels are driven through a differential located between the engine and gearbox. The engine may have one or more cylinders canted at least five degrees to the vertical; and may be mid-mounted. The engine may be mounted substantially behind the seating area. Road and/or marine drive trains may comprise at least one decoupler. Seating may be across the vehicle in one or more rows, or in a tandem layout. A central driving position may be provided.

Description

An Amphibious Vehicle

The present invention relates to an amphibious vehicle having a hull conformed to enable planing.

The power required to enable an amphibious vehicle to plane is considerable and it is therefore very important to reduce drag; as distinct from a displacement vehicle, where speed is not so important Drag caused by the vehicle's road wheels may be reduced by suitable drag reduction means such as fairings, which mostly or wholly cover the road wheels; or else the road wheels are retractable. Marine propulsion units with reversing buckets such as shown in US Patent No 3,756,185 (Breslin) have been proposed for amphibious planing vehicles. However, the buckets and associated control gear themselves cause drag.

Accordingly, an amphibious vehicle in accordance with the invention which has a hull confirmed to enable planing, road wheels with drag reduction means and at least one marine propulsion unit, is provided with an engine having an engine output shaft aligned fore and aft and arranged to drive a gearbox having a reversible output, this reversible output arranged to drive at least some of the road wheels and the marine propulsion unit, wherein the reversible output is arranged to drive the road wheels through a differential located between the engine and gearbox.

The drag reduction means may be either fairings for the wheels, or preferably retractable wheels. The provision of the differential between the engine and gearbox ensures the centre of gravity of the power train is kept as low as possible. Hence the vehicle has a low metacentric height, which is important for stability. The position of the differential between engine and gearbox also assists packaging by ensuring that the differential does not intrude into the area where the marine drive and water intake are located for an aft-mounted water jet. The provision of a reversing drive to the marine propulsion unit is effective in reducing drag, as it is not essential to fit a reversing bucket. Furthermore when on the plane, where power can be reduced, it is possible to use - where fitted - a gearbox overdrive to increase the marine propulsion speed relative to the engine speed. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic side view of a vehicle according to the invention with wheel fairings or retraction;

Figure 2 is a plan sectional view of the vehicle of Figure 1;

Figure 3 is a longitudinal sectional view of the arrangement of engine, gearbox, road wheel and marine drive for the vehicle of Figure 1;

Figure 4 is a cross section of the vehicle of Figure 2 taken on line IV - IV of that figure, showing the disposition of engine and retractable wheels;

Figure 5 is a similar cross section to Figure 4, showing the same disposition of engine and retractable wheels, but for a second embodiment with the engine having one or more canted bank(s) of cylinders;

Figure 6 is a plan sectional view similar to Figure 2, showing an alternative power train and interior seating layout according to the second embodiment of Figure 5;

Figure 7 shows diagrammatically a vehicle being a third embodiment of the invention; and

Figure 8 shows diagrammatically a vehicle being a fourth embodiment of the invention.

In Figures 1 and 2, an amphibious vehicle 1 is shown having retractable front wheels 2 and retractable rear wheels 3; or as shown in broken lines at 12 and 13, retractable fairings. The wheel retraction or fairings constitute drag reduction means. Vehicle 1 has a hull 4 conformed for planing, to which end the engine 18 with its associated reversible gearbox 63 are mounted towards the rear of the vehicle. As shown in the figures, the engine is mounted just in front of the rear axle; this is known as a mid- engine configuration; or as a mid-mounted engine. It will also be noted that the engine is mounted North-South, that is, with the flywheel towards the rear of the vehicle. Driven from gearbox 63 (see Figure 3) through gears 46 on input shaft 44, and gears 48 on output shaft 50, are transaxle differential 24 and marine propulsion unit 40 with impeller 38. The impeller is driven from gearbox 63 by synchromesh unit 65 in housing 61. Unit 65 functions as a decoupler to decouple drive gear 58, which is coupled to the impeller 38 by driveshaft 36 and constant velocity joint 56. In order to decouple the rear wheels 3 from the transaxle differential 24, allowing marine drive only, decouplers 70 (Figures 4 and 5) are provided for halfshafts 72.

Figure 4 shows a cross section of the vehicle, and particularly the conformation of the planing hull 4. The engine 18 is mounted as low as possible to improve die marine stability. A particular advantage of a longitudinally mounted engine in a planing vehicle may be seen from this figure. In a planing vehicle, the hull must have a deadrise to allow planing; that is, the two sides of the hull slope upwards from a low point on the longitudinal centre line. A longitudinal engine can be mounted lower in the vehicle than a transverse engine, because the engine sump - conventionally the lowest point on the engine - can be fitted into the lowest part of the hull. With a transverse engine layout, as shown for example in the applicant's co-pending application published as WO 02/07999, the sump must be mounted or adapted to clear the deadrise of the hull.

With the engine mounted as low as is possible in the hull, the centre of gravity of the power train, and therefore of the vehicle, is made as low as possible, with beneficial effects on roadholding and on-road handling and stability. On water, the determinant of vehicle stability is metacentric height - the vertical distance between the centre of gravity and the centre of buoyancy, discussed at length in WO 02 07999. The greater this height, the more stable the vehicle. Hence, an engine mounted as shown in Figure 4, where the sump can be contained within the lowest part of the hull, offers handling advantages both on road and on water.

Figure 5 shows a second embodiment of the amphibious vehicle according to the invention, with a further refinement to improve vehicle stability. In this case, the engine block 18' is canted to one side to lower the centre of gravity, and increase the metacentric height, still more than with a power train laid out according to Figure 4.

Referring back to Figure 2, a drawback of the amphibious vehicle according to the first embodiment of the invention may be seen. Due to the longitudinal mounting of the engine, there is only space for two seats 14 and 15, which are widely spaced across the vehicle. This may be acceptable in a racing amphibious vehicle, taking full advantage of the great stability offered by a low centre of gravity. However, this may not be acceptable in a production vehicle, for social reasons. In this context the market failure of the Hobbycar amphibious vehicle, which had seating spaced apart across and along the vehicle, should be noted.

In this context, a preferred arrangement of the Figure 5 embodiment has practical advantages. An engine 18" with a second canted cylinder bank ~ that is, a vee type engine - has a lower centre of gravity than an upright, inline engine; and will usually be shorter than an inline engine for the same power output. For example, a 2.5-litre V6 engine may develop 170PS with a shorter cylinder block and shorter piston, stroke than an inline 2.0- litre four cylinder developing 140PS. To develop the same power as the V6 engine, the four-cylinder engine would have to be supercharged or turbocharged. However, such forced induction can lead to heat dissipation problems on water, due to the lack of ram air effect, and the sealing of the underside of the engine bay necessary to ensure flotation.

Referring now to Figure 6, it can be seen that in an amphibious vehicle 81 with an engine 18" which is shorter than engine 18 in Figure 2, there is room for three seats 14, 15, and 16 across the vehicle. In this context, seat 16 may be a centrally mounted driver's seat. This layout gives a commanding view on water, and obviates the need to tool up for separate left- and right-hand drive versions of the amphibious vehicle. In a racing amphibious vehicle, seat 16 may be the only one fitted.

Figure 7 shows a third embodiment of the amphibious vehicle according to the invention. Vehicle 91 is essentially an amphibious bus, with several rows of seating 17, and retractable wheels 2' and 3' fore and aft. Engine 18 is mounted beneath the passenger compartment floor, as is known from land-based buses and coaches. In such a vehicle, a low engine height is helpful not only to lower the centre of gravity, but also to allow the lowest possible passenger floor. By containment of the entire power train within the rear part of the vehicle, there are two options for seating and luggage space. As shown in the figure, rows of seating 17 may be mounted on the level, and space 92 used for luggage; alternatively, theatre type seating may be fitted, with the foτemost seats low down and the rearmost seats highest, to allow the passengers at the back of the vehicle to see out forwards. In either case, the shorter and lower the engine the better; so a canted engine 18'according to Figure 5, or a vee type engine 18" corresponding to Figures 5 and 6, will be found particularly suitable for this vehicle.

Figure 8 shows a narrow amphibious vehicle 101, with one or more retractable front wheels 2", and retractable rear wheels 3". In such a narrow vehicle, it is difficult to find space for a single, central marine drive and a single rear wheel. Therefore two rear wheels are needed; and so in turn, a differential is required. However, the width of the vehicle, particularly where there is only a single front wheel, is such that there is room for only one seat across the vehicle. The Figure shows tandem type seating, with a passenger located behind the driver. Such seating would conventionally be on or adjacent to the longitudinal centre line of the vehicle. In this embodiment, there is clearly a compromise between seating height and the width of the engine bay. In this context, an engine such as the Volkswagen VR6 engine, with a fifteen degree angle between its cylinder banks, is shorter than an inline six, but narrower than a conventional V-6 engine, with an angle of sixty or even ninety degrees between its banks. Packaging studies have shown that a vee angle of as little as ten degrees between two cylinder banks can be beneficial in packaging the power train and vehicle occupant or rider accommodation. Hence, a cylinder bank angle of as little as five degrees from the vertical can be beneficial to packaging.

Further variations of the embodiments described above may be made without departing from the essential inventive concept described. For example, any or all of the decouplers described above may comprise a constant velocity joint and synchromesh unit, as described in the applicant's co-pending application, published as WO 02/14092. The wheel driveshafts may also be decoupled by one decoupler only; as the other halfshaft may be locked by use of the vehicle handbrake on water. Although a mid engined layout is described, a front mounted engine could be used if a suitable weight distribution for planing could be achieved. Similarly, a four wheel drive layout could be provided by a suitable power take off or transfer case from the transmission. A flat engine, that is one having opposed horizontal banks of cylinders, could be used; although difficulties can be foreseen with maintenance access, and with routing of exhaust pipes and/or fuel and air inlet piping. A propeller marine drive, or twin jet drive, could be arranged. Where a central driving position is provided, a seat mounting arrangement according to the applicant's co- pending application OB0218604.7 may be found beneficial. Although a manual gearbox is shown in the figure, a semi-automatic, fully automatic, or CVT (continuously variable transmission) may be found equally suitable for both road and marine purposes. Finally, although faired wheels are shown at both front and rear of the Figure 1 embodiment, it may only be necessary when planing to fair the rear wheels.

Claims

An amphibious vehicle having a hull conformed to enable planing, road wheels with drag reduction means, and at least one marine propulsion unit, the vehicle being provided with an engine having an engine output shaft aligned fore and aft and arranged to drive a gearbox having a reversible output, the reversible output being arranged to drive at least some of the road wheels and the marine propulsion unit, wherein the reversible output is arranged to drive the road wheels through a differential located between the engine and the gearbox.

A vehicle as claimed is claim 1 wherein the drag reduction means is provided by an arrangement to retract the wheels.

3. A vehicle as claimed in claim 1 wherein the drag reduction means is provided by an arrangement to fair at least the rear wheels.

4. A vehicle as claimed in any one of the preceding claims wherein the engine comprises at least one cylinder canted at an angle of at least five degrees to the vertical.

5. A vehicle as claimed in any one of the preceding claims wherein the engine is mid-mounted.

6. A vehicle as claimed in any one of the preceding claims wherein the engine is mounted with its flywheel towards the rear of the vehicle.

7. A vehicle as claimed in any one of the preceding claims wherein the engine and gearbox are at least mostly located behind the seating for the driver and passenger(s).

8. A vehicle as claimed in any one of claims I to 6 wherein the engine and gearbox are at least mostly located below the seating for the driver and passenger(s).

9. A vehicle as claimed in any one of the preceding claims wherein the driver's seat is mounted centrally in the width of the vehicle.

10. A vehicle as claimed in any one of the preceding claims wherein the driver's seat and at least one passenger seat are mounted in tandem on or adjacent to the longitudinal centre line of the vehicle.

11. A vehicle as claimed in any one of the preceding claims wherein the driven road wheel(s) is/are driven through at least one decoupler.

12. A vehicle as claimed in any one of the preceding claims wherein the marine drive unit(s) is/are driven through at least one decoupler.

13. An amphibious vehicle substantially as described with reference to any one or more of the accompanying drawings.